In order to find the area of the triangle in question, it is best to plot the vertices, to find what segment is the base and what is its height.
Please allow me a little time to plot this triangle.
Once we have the triangle plotted, we can easily decide that the vertical segment that joins the points (4, 3) and (4, -2) is going to be our base for the formula of the area of a triangle:
Base = distance between 3 and -2 = 5 units. Base = 5 units.
The height is going to be given by the distance fron the vertex further to the left (-1, -5) to the line where the base is (the vertical line through x = 4). Then this height is 4 - -1 = 5
Then the area of the trianglke based on the formula:
Area = Base x Height / 2 becomes:
Area = 5 x 5 / 2 = 25 / 2 = 12.5 square units.